BIO THE ELECTRIC EGG. Upon fertilization, the eggs of many species undergo a rapid change in potential difference across their outer membrane. This change affects the physiological development of the eggs. The potential difference across the membrane is called the membrane potential, Vm, which is the potential inside the membrane minus the potential outside it. The membrane potential arises when enzymes use the energy available in ATP to expel three sodium ions (Na+) actively and accumulate two potassium ions (K+) inside the membrane—making the interior less positively charged than the exterior. For a sea urchin egg, Vm is about −70 mV; that is, the potential inside is 70 mV less than that outside. The egg membrane behaves as a capacitor with a capacitance of about 1 μF/cm2. The membrane of the unfertilized egg is selectively permeable to K+; that is, K+ can readily pass through certain channels in the membrane, but other ions cannot. When a sea urchin egg is fertilized, Na+ channels in the membrane open, Na+ enters the egg, and Vm rapidly increases to +30 mV, where it remains for several minutes. The concentration of Na+ is about 30 mmol/L in the egg’s interior but 450 mmol/L in the surrounding seawater. The K+ concentration is about 200 mmol/L inside but 10 mmol/L outside. A useful constant that connects electrical and chemical units is the Faraday number, which has a value of approximately 105 C/mol; that is, Avogadro’s number (a mole) of monovalent ions, such as Na+ or K+, carries a charge of 105 C.
24.73 How many moles of Na+ must m ove per unit area of membrane to change Vm from −70 mV to +30 mV, If we assume that the membrane behaves purely as a capacitor? (a) 10 −4 mol/cm2; (b) 10−9 mol/cm2; (c) 10−12 mol/cm2; (d) 10−14 mol/cm2.
Want to see the full answer?
Check out a sample textbook solutionChapter 24 Solutions
University Physics (14th Edition)
Additional Science Textbook Solutions
Sears And Zemansky's University Physics With Modern Physics
Physics: Principles with Applications
Essential University Physics (3rd Edition)
Tutorials in Introductory Physics
Modern Physics
Essential University Physics: Volume 1 (3rd Edition)
- Rank the potential energies of the four systems of particles shown in Figure CQ16.4 from largest to smallest. Include equalities if appropriate. Figure CQ16.4arrow_forwardAt locations A and B, the electric potential has the values VA = 1.59 V and VR = 5.87 V, respectively. A proton released from rest at one of these locations passes through the other location. From which location was the proton released? A В What is its speed when it passes through the other location? speed: m/s Repeat the same question, but this time for an electron. From which location was the electron released? A B What is its speed when it passes through the other location? speed: m/sarrow_forwardA potential difference AV exists between the inner and outer surfaces of the membrane of a cell. The inner surface is negative relative to the outer surface. If 1.50 × 10-20 J of work is required to eject a positive potassium ion (K*) from the interior of the cell, what is the magnitude of the potential difference (in millivolts) between the inner and outer surfaces of the cell? |AV| = mVarrow_forward
- A potential difference of 75 mV exists between the inner and outer surfaces of a cell membrane. The inner surface is negative relative to the outer surface. How much work is required to eject a positive sodium ion (Na+) from the interior of the cell?arrow_forwardRank the potential energies of the four systems of particles shown in Figure CQ16.4 from largest to smallest. Include equalities if appropriate. -Q -Q 20 a -20 2r -Q 2r Figure CQ16.4arrow_forwardplease answer this questionarrow_forward
- A potential difference of 102 mV exists between the inner and outer surfaces of the membrane of a cell. The inner surface is negative relative to the outer surface. How much work is required to eject a positive sodium ion (Na+) from the interior of the cell?arrow_forwardAn electron accelerates from rest at point A with electric potential -1236x1010 v towards point B at electric potential 8948×1010 v. The decrease in potential energy of the electron in units of nJ equals:arrow_forwardA proton moves from a location where the electric potential is 25 V to a location where the electric potential is 10 V. What is the change in the proton’s kinetic energy?arrow_forward
- Write a question about the electrical action potential of the human nervous system in terms of physics.arrow_forwardEvery cell in the body has organelles called mitochondria that can generate a voltage difference between their interior and exterior. If the capacitance of a mitochondrion is 4.0×10−11F and the potential difference between the interior and exterior is 0.18 V, how much electrical energy does it store? If a mitochondrion were to use all of its stored electrical energy to produce ATP molecules, and each ATP molecule requires 9.5×10−20J, how many molecules could it produce? (In reality, ATP molecules are produced by the flow of protons caused by the proton motive force, and not by the direct conversion of electrical energy stored by the capacitance of mitochondria.)arrow_forwardPart A and B please Electronic flash units for cameras contain a capacitor for storing the energy used to produce the flash. In one such unit, the flash lasts for a time interval of 1.48×10−3 s with an average light power output of 2.70×105 W. Part A If the conversion of electrical energy to light has an efficiency of 92.0 %(the rest of the energy goes to thermal energy), how much energy must be stored in the capacitor for one flash? Part B The capacitor has a potential difference between its plates of 140V when the stored energy equals the value calculated in part A. What is the capacitance?arrow_forward
- College PhysicsPhysicsISBN:9781305952300Author:Raymond A. Serway, Chris VuillePublisher:Cengage LearningCollege PhysicsPhysicsISBN:9781285737027Author:Raymond A. Serway, Chris VuillePublisher:Cengage LearningPhysics for Scientists and Engineers: Foundations...PhysicsISBN:9781133939146Author:Katz, Debora M.Publisher:Cengage Learning
- Principles of Physics: A Calculus-Based TextPhysicsISBN:9781133104261Author:Raymond A. Serway, John W. JewettPublisher:Cengage Learning